EU stands firm on nuclear freeze

But they cautioned the tentative deal between Britain, France, Germany and Iran could still collapse as Tehran had yet to give its final approval to the agreement, which was still being finalised.

A spokeswoman for the UN nuclear watchdog said the agency's meeting had adjourned until Monday to allow time for the parties to clarify their positions.

A diplomat close to the talks said more work remained to be done by Iran. Asked how soon that might happen, the diplomat said: "Not for some days yet. They are famous for coming out with different things at the last minute."

Last week, Iran promised the European Union it would halt all activities related to uranium enrichment, a process that creates atomic fuel for power plants or weapons, in a bid to neutralize the threat of economic sanctions.

The ink on the hard-won accord was barely dry, however, when Tehran demanded an exemption for some 20 enrichment centrifuges for research purposes. Western diplomats said this was impossible and could only deepen suspicions that Tehran has a secret weapons program, as Washington alleges.